A conventional apparatus for measuring water content in foundry sand by applying an electric current to the foundry sand uses a device of electrodes to supply the electric current to it. The device of the electrodes is comprised of a plurality of elements of electrodes disposed parallel to each other with certain intervals between them, wherein the elements form a square bar and have electrical conductivity, a retaining element to retain the plurality of the elements of the electrodes so that the upper surfaces of the elements of the electrodes are exposed, wherein the retaining element has an electrical insulating property, and connecting means to alternately connect the plurality of the elements of the electrodes to each other so that the connected elements of electrodes form two poles, wherein the means have electrical conductivity.
However, for the conventional device for measuring the water content in foundry sand having the above constitution, when it is disposed in a hopper storing the foundry sand, a rather large space is required in the hopper.
Here, “water content in foundry sand” is defined as an amount of water contained in it and expressed as a percentage of the weight of the water in the foundry sand of a unit weight. It is possible to control the properties of return foundry sand so that it has the optimum properties as foundry sand used for molding a mold by measuring the water content in the foundry sand.
Patent document 1: WO 2004/003534 A1